Filtering device for equipping a ventilation and/or heating and/or air conditioning unit, more particularly for a motor vehicle

ABSTRACT

A filter device has a frame, a grid, a filter medium and, if desired, a gas adsorption medium. The frame is flexible so as to be temporarily deformable and is made of polypropylene, as is the grid. The filter medium is a mat of non-woven material and the gas adsorption medium is activated carbon.

BACKGROUND OF THE INVENTION

The present invention relates to a filter device for equipping anapparatus for ventilating and/or heating and/or air conditioning, moreparticularly for a vehicle.

A first object of the invention is to improve the efficiency and usefullife of such a filter device.

Another object of the invention is to make it easier to change thefilter device when it is clogged.

Yet another object of the invention is to make it easier to recycle sucha filter device, in particular where the filter includes means foradsorbing harmful gases.

BRIEF SUMMARY OF THE INVENTION

These objectives are obtained by one or other of the following featuresof the invention, and by any of their technically possible combinations:

the filter device includes a flexible grid which is surrounded by arelatively flexible frame;

a mat of non-woven material, comprising of a carded web, is appliedagainst the grid and constitutes a particle filter;

the mat of non-woven material comprising of a carded web is appliedagainst the grid without being fixed to the latter;

the carded web constitutes a single fabric layer;

the carded web is placed upstream of the grid in relation to the normaldirection of flow of the gas to be filtered;

the filter device includes gas adsorption means placed between the gridand the non-woven mat;

the adsorption means comprise an activated carbon tissue;

the activated carbon tissue is flexible;

the adsorption means comprise a bed of activated carbon;

a mat of non-woven material, comprising of a carded web, is disposed oneither side of the adsorption means;

a second grid, being a so-called inlet grid, is disposed upstream of themat of non-woven material;

both grids are of the same nature;

the two grids are of different natures;

at least one of the dimensions of the carbon tissue and preferably eachof them, is smaller than the corresponding dimensions of the grid oreach grid and that of the frame, so that on at least one side of thecarbon tissue, the latter is at least partially spaced away from theframe;

one grid, or preferably both grids, are pleated;

the non-woven mat is pleated;

the carbon tissue is pleated;

the grid is of polypropylene;

the second grid is of polypropylene;

the mat of non-woven material is based on long fibres, the length ofwhich is preferably at least 38 mm;

the long fibres have a mean diameter which at least 10 μm;

the fibres are of thermoplastic material;

the fibres are polypropylene fibres;

the frame is of polypropylene foam or porous polypropylene;

the frame is fixed to the grid by mirror welding

the frame is fixed to the outlet grid, and also to the second grid, bymirror welding;

the frame is moulded over the grid;

the frame is moulded over the grid and over the mat of non-wovenmaterial;

the frame is also moulded over the second grid;

all or some of the lateral ends of the grid are curved in such a way asto follow the corresponding wall or walls of the frame.

The filter device in accordance with the invention has improvedefficiency and offers a reduced loss of energy in the air to be filteredthan do the filters in the state of the art.

In addition, the filter device according to the invention is preferablyin the form of a flexible cassette, which is such that it can bedeformed temporarily in all directions while being inserted or removedin an apparatus for ventilating and/or heating and/or air conditioning,which considerably facilitates the corresponding operations, especiallywhere accessibility to the housing of the filter device is, as is mostcommonly the case, not easy to obtain.

Thanks to the construction of the filter device according to theinvention, the assembly of the various parts of the filter can becarried out without making use of any solvent or adhesive, whileexcellent sealing is obtained between the frame and the various activeparts of the filter.

The flexibility of the frame advantageously enables it to be sealed atits periphery without there being any need to provide a sealing gasket.

In addition, the flexibility of the frame contributes to the preventionand absorption of vibrations and noises in the filter, and in the ductin which the filter is placed.

After use, the filter device according to the invention can easily berecycled after its various component parts have been separated from eachother, which is facilitated in particular when the carbon tissue is outof contact with the frame.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the invention will appear in thedescription of embodiments thereof, given below by way of example andwith reference to the attached drawings, which show:

in FIG. 1, a diagrammatic view in cross section, showing part of afilter device according to the invention;

in FIG. 2, a view similar to that in FIG. 1 but corresponding to anotherembodiment of the invention;

in FIG. 3, a front view of the filter device of FIG. 2;

in FIGS. 4 and 5, diagrammatic views which illustrate the fastening of agrid to the frame of the filter device;

in FIGS. 6a and 6 b, an illustration of the properties of flexibility ofthe filter;

in FIGS. 7 and 8, a diagrammatic view of the manufacture of the filterdevice according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The filter device 1 of FIG. 1 comprises a flexible grid 2 of pleatedform, against which there is disposed, without being fixed a filtermedium 3 which constitutes a particle filter in the form of a non-wovenmat, comprising of a carded web and a single fabric layer. The filtermedium 3 is itself pleated in the same way as the grid 2.

The non-woven mat comprises long fibres, the length of which ispreferably at least 38 mm. The said long fibres have a mean diameterwhich is at least 10 μm. The fibres are of thermoplastic material and,in practice, are polypropylene.

The grid 2 is of polypropylene. It is located downstream with respect tothe direction F of flow of the air in the filter device.

In the example in FIG. 1, a pleated, flexible second grid 5 is arrangedin such a way that the filter medium 3 is placed between the grids 2 and5 without being fixed to either one of these two grids 2 and 5.

Preferably, the second grid, which is a so-called inlet grid, is locatedupstream of the medium 3 in the direction F of flow of the air in thefilter device.

Preferably, the second grid 5 is of the same nature as the grid 2, andis of polypropylene.

In another version, the two grids 2 and 5 are of different natures.

The filter device of FIG. 1 is a particle filter.

The invention is also concerned with a so-called combined filter, aparticle filter in combination with a filter for blocking harmful gases.

In that case, gas absorption means 4 are added to the base structure ofFIG. 1 comprising of the downstream grid 2 and the medium 3, and areplaced between the grid 2 and the medium 3 in such a way as to be in thefollowing succession in the direction F of flow of the air: medium 3,gas adsorption means 4, and the flexible grid 2 downstream.

FIG. 2 shows a combined filter which includes, in succession in thedirection F of flow of the air: an inlet grid 5, a medium 6, gasadsorption means 4, a medium 3 and an output grid 2. The media 3 and 6are preferably of the same nature, as described above. Accordingly, eachof two non-woven mats 3 and 6 is in the form of a carded web, and theseare disposed respectively on either side of the gas adsorption means 4.

The gas adsorption means may comprise a bed of activated carbon, butpreferably, and as shown in FIG. 2, comprises a pleated tissue offlexible carbon, pleated in the same way as the grid 2 or 5 and themedium 3 or 6.

The filter device of FIG. 2 has a symmetrical construction which has theadvantage that it can be fitted indifferently in either one direction orthe other in an apparatus for heating and/or ventilating and/or airconditioning, which makes it unnecessary to provide any indexing meansto determine the fitting direction. The filter device is thusreversible. In this case, the inlet grid may of course act as an outletgrid, and conversely the outlet grid may act as an inlet grid.

A flexible frame is arranged to support the various components of thefilter device. One such flexible frame is shown at 7 in FIG. 3. AlthoughFIG. 3 corresponds to the embodiment of FIG. 2, the arrangements inrelation to the frame described below are also applicable to otherembodiments, and in particular to the embodiment described withreference to FIG. 1.

The frame 7 is made of polypropylene foam or, in another version, ofporous polypropylene, and is fixed to the outlet grid 2 or the inletgrid 5, and preferably to both of the grids 2 and 5 where both arepresent.

The fastening of a grid 2 or 5 to the frame 7 is preferably obtained, asindicated diagrammatically in FIGS. 4 and 5, by a so-called mirrorwelding operation which consists in simultaneously heating, up to theonset of melting, a peripheral portion 8 of the grid 2 or 5 on the onehand, and a portion 9 of the frame 7 corresponding to the fastening zoneon the other hand, and then bringing together and clamping against eachother the above mentioned peripheral portion 8 and portion 9, such thata relative pressure is exerted as indicated diagrammatically by thearrows P in FIG. 5.

The mirror welding operation is performed in such a way that the lateralend 8 of the grid 2 or 5 is caused to bend at a right angle so as tofollow the form of the corresponding internal face of the frame 7, whichadvantageously improves fastening of the grid and avoids any leakage ofair between the grid and the frame.

Preferably, a plurality of peripheral portions 8 and correspondingportions 9, and preferably all four of the grid 2 or 5 and the frame 7,are fixed together in this way.

As is shown in FIG. 3, the two grids 2 and 5 are fixed to the frame 7 inthe manner just described.

The fact that the grid 2 or 5 and the frame 7 are of the same chemicalnature (polypropylene) enables the fastening to be solid and durable.

During the mirror welding operation, the non-woven mat or mats are laidagainst the corresponding grid or grids 2 and/or 5, with, if necessary,adsorption means 4, such as, and preferably, carbon tissue, interposedin the manner described above.

In another version not shown, the frame is moulded around the grid 2 or5, or around both of the grids 2 and 5, and also on the filter medium ormedia 3 and/or 6.

In accordance with a major aspect of the invention, the adsorption means4, which are preferably in the form of an activated carbon tissue,extend on at least one side, and preferably on all four sides, by anamount which is smaller than that of the grid 2 and/or 5 and preferablyalso smaller than that of the filter medium 3 and/or 6. This can be seenin FIG. 3, in which it can be observed that the dimensions of theactivated carbon tissue 4 are smaller than those of the grids 2 and 5and the filter media 3 and 6.

As a result, the adsorption means are spaced away from the frame 7. Thishas the advantage that the presence of the adsorption means does notdisturb the fastening of the grids to the frame, and when a used filteris being recovered it is easily possible, by sectioning the grid orgrids, to recover the adsorption means which are a major element in theselling price of a filter, so that they can be regenerated and reused ina new filter.

By virtue of the way the filter is made, as described above, the latterhas important features of flexibility which enable it to be curvedmomentarily as shown in FIGS. 6a and 6b, or even to be bent, in orderthat the filter can more easily be introduced into or removed from forheating and/or ventilating and/or air conditioning a motor vehicle. Thisis of particular advantage where, as is very often the case,accessibility to the housing of the filter is difficult to achieve.

FIGS. 7 and 8 illustrate a preferred method of making a filter device asdescribed above.

Polypropylene filters having a fineness of 1.7 dtex (diameter 14 μm),cut to a length of 40 mm, are introduced into a mixer.

The mixture of fibres obtained is then introduced into a feeder 10 andthen into a storage silo 11, before being carded, into an isotropic cardweb by means of a wool-type card 12 with a double comb and equipped witha pell-mell type stirrer.

The web is, at the outlet of the card, introduced into a condenser 13 soas to form a fabric layer.

The parameters of the card and those of the condenser are so chosen thata fabric layer is obtained which has a surface density of about 20 atabout 150 g/m².

The fabric layer is deposited on a carpet and is then consolidated bymeans of an hydraulic binding operation at 14.

The hydraulic binding operation consists in passing the fabric layer,disposed on a rotating drum, through very fine water jets under highpressure (40 to 200 bar).

By rebounding on the drum, the water jets cause the fibres to knittogether, which gives to the fabric layer a high mechanical strengthwithout increasing its density.

After being passed through a drying tunnel 15, the fabric layer isrolled up at 16.

The fabric layer is subsequently undergoes a pleating operation at 18,and is then ready to be cut into sections 9 and to be mounted on asupport so as to form the filter device described above.

In accordance with the invention, the filter device comprises a fabriclayer of a single layer.

In that connection, with a fabric layer 0.84 mm thick, it has beenpossible to make a filter which has a surface density of 66 g/m² andwith a density of 0.07.

In order to test the effectiveness of the filter made in this way, thefilter was placed across a passage having a cross section equal to 100cm², with a stream of air charged with particles being passed through itat a velocity of 20 cm/s.

The particles were those of a powder of the so-called “SAE fine powder”type, which is defined by Standard SAE J726/ISO5011 of the United Statesof America.

The concentration of the particles was 100 mg/m³.

It was found that the loss of energy on passing through the filter underthese conditions was only 14 Pa, and that efficiency reaches 80%.

As to filter devices currently on the market, an efficiency was obtainedcomparable to the best of these, but with a product having a much lowerdensity (0.07, as against 0.12 to 0.30) and giving rise to a generallysmaller loss of energy.

Endurance tests have, in addition, shown improved stability, over time,in the efficiency of the filter device in accordance with the invention.

What is claimed is:
 1. A filter for a climate control apparatuscomprising a frame, a first grid, and a filter medium, wherein the frameand the first grid are flexible such that the filter is able to betemporarily deformed in all directions while being inserted in orremoved from said climate control apparatus.
 2. A filter according toclaim 1, wherein the first grid is made of polypropylene.
 3. A filteraccording to claim 1 wherein the frame is polypropylene.
 4. A filteraccording to claim 1, wherein the frame is a foam material.
 5. A filteraccording to claim 1, wherein the filter medium comprises a mat ofnon-woven carded web material.
 6. a filter according to claim 5, whereinsaid mat of non-woven carded web material is applied against the firstgrid without being fixed to the first grid.
 7. a filter according toclaim 6, wherein said mat constitutes a single fabric layer.
 8. a filteraccording to claim 7, wherein said climate control apparatus has anormal direction of flow of gas to be filtered and wherein said mat isplaced upstream of the first grid in relation to the normal direction offlow of the gas to be filtered.
 9. A filter according to claim 5,wherein the mat of non-woven carded web material is based on long fibreshaving a length greater than about 38 mm.
 10. A filter according toclaim 9, wherein the long fibres have a mean diameter which issubstantially at least 10 μm.
 11. A filter according to claim 10,wherein the long fibres are polypropylene fibres.
 12. a filter accordingto claim 9, wherein the long fibres are thermoplastic material.
 13. Afilter according to claim 1, which further comprises a gas adsorptionmember placed between the first grid and the filter medium.
 14. A filteraccording to claim 13, wherein the adsorption member comprises anactivated carbon tissue.
 15. A filter according to claim 14, wherein theactivated carbon tissue is flexible.
 16. A filter according to claim 14,wherein the first grid and the activated carbon tissue are pleated. 17.A filter according to claim 14, wherein at least one dimension of theactivated carbon tissue is smaller than a corresponding dimension of thefirst grid and a corresponding dimension of the frame so that on atleast one side of the activated carbon tissue, the activated carbontissue is at least partially spaced away from a side of the frame.
 18. Afilter according to claim 13, wherein said adsorption member comprises abed of activated carbon.
 19. A filter according to claim 13, whichfurther comprises a second filter medium disposed between the first gridand said adsorption member.
 20. A climate control apparatus includingthe filter of claim
 19. 21. A filter according to claim 13, wherein asecond grid is disposed upstream of the filter medium.
 22. a filteraccording to claim 21, wherein said first grid and said second grid areof the same nature.
 23. A filter according to claim 21, wherein theframe is fixed to the first grid and the second grid by mirror welding.24. A filter according to claim 21, which is of symmetricalconstruction, and reversible.
 25. A filter according to claim 1, whereinthe frame is fixed to the first grid by mirror welding.
 26. A filteraccording to claim 25, wherein at least one lateral end of the firstgrid is curved in such a way as to follow a corresponding wall of theframe.
 27. A filter according to claim 1, wherein the frame is mouldedover the first grid.
 28. a filter according to claim 27, wherein theframe is moulded over the filter medium.
 29. A filter device for aclimate control apparatus having a normal flow direction for gas that isto be filtered therein, said filter comprising: a frame, said frameflexible and temporarily deformable; a first grid, said first gridflexible and temporarily deformable; and a first filter mediumcomprising a single-fabric-layer mat of non-woven carded web material,said first filter medium positioned adjacent said first grid, said firstgrid and said first filter medium held within said frame.
 30. The filterdevice according to claim 29 wherein said first grid and said frame aremade of polypropylene or a foam material.
 31. The filter deviceaccording to claim 29 further comprising a gas adsorber positionedbetween said first grid and said first filter medium, said gas adsorbercomprising a flexible activated carbon tissue or a flexible bed ofactivated carbon.
 32. The filter device according to claim 31 whereinsaid first filter medium is positioned upstream of said first grid inrelation to said normal flow direction, the filter device furthercomprising a second filter medium comprising a single-fabric-layer matof non-woven carded web material, said second filter medium positionedbetween said gas adsorber and said first grid.
 33. The filter deviceaccording to claim 32 further comprising a second grid, said second gridpositioned upstream of said first filter medium.
 34. The filter deviceaccording to claim 33 wherein said first grid, said second filtermedium, said gas adsorber, said first filter medium and said second gridare pleated.
 35. The filter device according to claim 29 wherein atleast one dimension of said first filter medium is smaller than acorresponding dimension of said first grid and a corresponding dimensionof said frame so that at least one side of said first filter medium isat least partially spaced from a side wall of said frame.
 36. The filterdevice according to claim 29 wherein said first filter medium iscomprised of thermoplastic fibres having a length greater than about 38mm and a mean diameter substantially at least 10 μm.
 37. The filterdevice according to claim 29 wherein said frame is fixed to said firstgrid via mirror welding.
 38. The filter device according to claim 29wherein a lateral end of said first grid is curved to correspond to thecontour of a side wall of said frame.